Homeless children include
those who meet the definition contained in the HEARTH act of 2009:

• Someone who lacks a fixed, regular, and adequate nighttime residence.
• Someone who has as a primary nighttime residence a public or private place not designed for or ordinarily used as a regular sleeping accommodation for human beings, including a car, park, abandoned building, bus
  or train station, airport, or camping ground.
• Someone living in a supervised publicly or privately
  operated shelter designated to provide temporary living arrangements.
• Someone who resided in a shelter or place not meant for
  human habitation and who is exiting an institution where he or she temporarily
  resided.
• Someone who will imminently lose their housing, including
  housing they own, rent, or live in without paying rent, are sharing with
  others, and rooms in hotels or motels, has no subsequent residence identified,
  and lacks the resources or support networks needed to obtain other permanent housing.
• A family that has experienced a long-term period without
  living independently in permanent housing, has experienced persistent
  instability as measured by frequent moves over such period, and can be expected
  to continue in such status for an extended period of time because of chronic
  disabilities, chronic physical health or mental health conditions, substance
  addiction, histories of domestic violence or childhood abuse, the presence of a
  child or youth with a disability, or multiple barriers to employment.